Pneumatic impact drilling tool

Abstract

A pneumatically operated impact drilling tool for earth drilling, includes a reciprocating hammer, an anvil positioned under the hammer and a feeder tube extending through the hammer. The drilling tool is connected to a string of drilling pipe and high pressure compressed air or other pneumatic fluid is introduced to operate the tool. The feeder tube directs the flow of fluid through ports in the hammer to alternate pressure on opposite sides of the hammer to move the same upward and downward relative to the anvil. An elastomeric check valve is positioned inside the upper end of the feeder tube. The air inlet end of the tube is also provided with air jet passages extending upward and outwardly and having check valves operated in the outflow direction. A flow controlling washer may also be provided at the inlet to the check valve in the feeder tube.

I claim: 
     
       1. An impact drilling tool for connection in a string of drilling pipe comprising an upper sub for connection to said drilling pipe,   a casing with an upper end connected to said upper sub,   an anvil member slidably positioned in the lower end of said casing and having a bit member on its lower end extending outside said casing,   a hammer piston in said casing above said anvil member for reciprocal movement longitudinally of said casing to strike said anvil member repeatedly.   a feeder tube for feeding compressed pneumatic fluid from said drilling pipe extending longitudinally of said casing through said hammer,   a plurality of passages and valve openings cooperable therewith in said feeder tube and said hammer piston to apply compressed pneumatic fluid to one end of said hammer piston when in one position and to the other end when said hammer piston is in another position, for effecting reciprocal movement thereof,   said casing and said sub defining an inlet chamber for receiving compressed pneumatic fluid in the inlet to said feeder tube,   at least one passageway in said tool opening from said inlet chamber diagonally through said sub to discharge pneumatic fluid upward and outward from said tool, and   a check valve positioned inside said passageway and opening to discharge fluid outside said tool and closing to prevent flow backward through said passageway into said tool.   
     
     
       2. A drilling tool according to claim 1 in which said check valve is a hollow tubular elastomeric material having a closed end with an opening operable to be flexed open upon application of internal pneumatic pressure. 
     
     
       3. A drilling tool according to claim 2 in which there are a plurality of said passageways. 
     
     
       4. A drilling tool according to claim 3 including an additional passageway including said feeder tube and a check valve positioned in the inlet end of said feeder tube comprising a hollow tubular elastomeric member having a closed end with an opening operable to be flexed open upon application of internal pneumatic pressure. 
     
     
       5. A drilling tool according to claim 1 including additionally an elastomeric deformable annular washer positioned in the end of said feeder tube adjacent said inlet chamber and ahead of said check valve and operable to be deformed into said feeder tube to restrict the same upon increasing pneumatic pressure applied thereto, thereby regulating the volume of flow to maintain the same substantially constant.